compiler/rustc_hir/src/definitions.rs

   1 //! For each definition, we track the following data. A definition
   2 //! here is defined somewhat circularly as "something with a `DefId`",
   3 //! but it generally corresponds to things like structs, enums, etc.
   4 //! There are also some rather random cases (like const initializer
   5 //! expressions) that are mostly just leftovers.
   6
   7 pub use crate::def_id::DefPathHash;
   8 use crate::def_id::{CrateNum, DefIndex, LocalDefId, StableCrateId, CRATE_DEF_INDEX, LOCAL_CRATE};
   9 use crate::hir;
  10
  11 use rustc_data_structures::fx::FxHashMap;
  12 use rustc_data_structures::stable_hasher::StableHasher;
  13 use rustc_data_structures::unhash::UnhashMap;
  14 use rustc_index::vec::IndexVec;
  15 use rustc_span::hygiene::ExpnId;
  16 use rustc_span::symbol::{kw, sym, Symbol};
  17
  18 use std::fmt::{self, Write};
  19 use std::hash::Hash;
  20 use tracing::debug;
  21
  22 /// The `DefPathTable` maps `DefIndex`es to `DefKey`s and vice versa.
  23 /// Internally the `DefPathTable` holds a tree of `DefKey`s, where each `DefKey`
  24 /// stores the `DefIndex` of its parent.
  25 /// There is one `DefPathTable` for each crate.
  26 #[derive(Clone, Default, Debug)]
  27 pub struct DefPathTable {
  28     index_to_key: IndexVec<DefIndex, DefKey>,
  29     def_path_hashes: IndexVec<DefIndex, DefPathHash>,
  30     def_path_hash_to_index: UnhashMap<DefPathHash, DefIndex>,
  31 }
  32
  33 impl DefPathTable {
  34     fn allocate(&mut self, key: DefKey, def_path_hash: DefPathHash) -> DefIndex {
  35         let index = {
  36             let index = DefIndex::from(self.index_to_key.len());
  37             debug!("DefPathTable::insert() - {:?} <-> {:?}", key, index);
  38             self.index_to_key.push(key);
  39             index
  40         };
  41         self.def_path_hashes.push(def_path_hash);
  42         debug_assert!(self.def_path_hashes.len() == self.index_to_key.len());
  43
  44         // Check for hash collisions of DefPathHashes. These should be
  45         // exceedingly rare.
  46         if let Some(existing) = self.def_path_hash_to_index.insert(def_path_hash, index) {
  47             let def_path1 = DefPath::make(LOCAL_CRATE, existing, |idx| self.def_key(idx));
  48             let def_path2 = DefPath::make(LOCAL_CRATE, index, |idx| self.def_key(idx));
  49
  50             // Continuing with colliding DefPathHashes can lead to correctness
  51             // issues. We must abort compilation.
  52             //
  53             // The likelyhood of such a collision is very small, so actually
  54             // running into one could be indicative of a poor hash function
  55             // being used.
  56             //
  57             // See the documentation for DefPathHash for more information.
  58             panic!(
  59                 "found DefPathHash collsion between {:?} and {:?}. \
  60                     Compilation cannot continue.",
  61                 def_path1, def_path2
  62             );
  63         }
  64
  65         // Assert that all DefPathHashes correctly contain the local crate's
  66         // StableCrateId
  67         #[cfg(debug_assertions)]
  68         if let Some(root) = self.def_path_hashes.get(CRATE_DEF_INDEX) {
  69             assert!(def_path_hash.stable_crate_id() == root.stable_crate_id());
  70         }
  71
  72         index
  73     }
  74
  75     #[inline(always)]
  76     pub fn def_key(&self, index: DefIndex) -> DefKey {
  77         self.index_to_key[index]
  78     }
  79
  80     #[inline(always)]
  81     pub fn def_path_hash(&self, index: DefIndex) -> DefPathHash {
  82         let hash = self.def_path_hashes[index];
  83         debug!("def_path_hash({:?}) = {:?}", index, hash);
  84         hash
  85     }
  86
  87     pub fn enumerated_keys_and_path_hashes(
  88         &self,
  89     ) -> impl Iterator<Item = (DefIndex, &DefKey, &DefPathHash)> + '_ {
  90         self.index_to_key
  91             .iter_enumerated()
  92             .map(move |(index, key)| (index, key, &self.def_path_hashes[index]))
  93     }
  94 }
  95
  96 /// The definition table containing node definitions.
  97 /// It holds the `DefPathTable` for `LocalDefId`s/`DefPath`s.
  98 /// It also stores mappings to convert `LocalDefId`s to/from `HirId`s.
  99 #[derive(Clone, Debug)]
 100 pub struct Definitions {
 101     table: DefPathTable,
 102
 103     // FIXME(eddyb) ideally all `LocalDefId`s would be HIR owners.
 104     pub(super) def_id_to_hir_id: IndexVec<LocalDefId, Option<hir::HirId>>,
 105     /// The reverse mapping of `def_id_to_hir_id`.
 106     pub(super) hir_id_to_def_id: FxHashMap<hir::HirId, LocalDefId>,
 107
 108     /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
 109     expansions_that_defined: FxHashMap<LocalDefId, ExpnId>,
 110 }
 111
 112 /// A unique identifier that we can use to lookup a definition
 113 /// precisely. It combines the index of the definition's parent (if
 114 /// any) with a `DisambiguatedDefPathData`.
 115 #[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
 116 pub struct DefKey {
 117     /// The parent path.
 118     pub parent: Option<DefIndex>,
 119
 120     /// The identifier of this node.
 121     pub disambiguated_data: DisambiguatedDefPathData,
 122 }
 123
 124 impl DefKey {
 125     pub(crate) fn compute_stable_hash(&self, parent: DefPathHash) -> DefPathHash {
 126         let mut hasher = StableHasher::new();
 127
 128         parent.hash(&mut hasher);
 129
 130         let DisambiguatedDefPathData { ref data, disambiguator } = self.disambiguated_data;
 131
 132         std::mem::discriminant(data).hash(&mut hasher);
 133         if let Some(name) = data.get_opt_name() {
 134             // Get a stable hash by considering the symbol chars rather than
 135             // the symbol index.
 136             name.as_str().hash(&mut hasher);
 137         }
 138
 139         disambiguator.hash(&mut hasher);
 140
 141         let local_hash: u64 = hasher.finish();
 142
 143         // Construct the new DefPathHash, making sure that the `crate_id`
 144         // portion of the hash is properly copied from the parent. This way the
 145         // `crate_id` part will be recursively propagated from the root to all
 146         // DefPathHashes in this DefPathTable.
 147         DefPathHash::new(parent.stable_crate_id(), local_hash)
 148     }
 149 }
 150
 151 /// A pair of `DefPathData` and an integer disambiguator. The integer is
 152 /// normally `0`, but in the event that there are multiple defs with the
 153 /// same `parent` and `data`, we use this field to disambiguate
 154 /// between them. This introduces some artificial ordering dependency
 155 /// but means that if you have, e.g., two impls for the same type in
 156 /// the same module, they do get distinct `DefId`s.
 157 #[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable)]
 158 pub struct DisambiguatedDefPathData {
 159     pub data: DefPathData,
 160     pub disambiguator: u32,
 161 }
 162
 163 impl DisambiguatedDefPathData {
 164     pub fn fmt_maybe_verbose(&self, writer: &mut impl Write, verbose: bool) -> fmt::Result {
 165         match self.data.name() {
 166             DefPathDataName::Named(name) => {
 167                 if verbose && self.disambiguator != 0 {
 168                     write!(writer, "{}#{}", name, self.disambiguator)
 169                 } else {
 170                     writer.write_str(&name.as_str())
 171                 }
 172             }
 173             DefPathDataName::Anon { namespace } => {
 174                 write!(writer, "{{{}#{}}}", namespace, self.disambiguator)
 175             }
 176         }
 177     }
 178 }
 179
 180 impl fmt::Display for DisambiguatedDefPathData {
 181     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 182         self.fmt_maybe_verbose(f, true)
 183     }
 184 }
 185
 186 #[derive(Clone, Debug, Encodable, Decodable)]
 187 pub struct DefPath {
 188     /// The path leading from the crate root to the item.
 189     pub data: Vec<DisambiguatedDefPathData>,
 190
 191     /// The crate root this path is relative to.
 192     pub krate: CrateNum,
 193 }
 194
 195 impl DefPath {
 196     pub fn make<FN>(krate: CrateNum, start_index: DefIndex, mut get_key: FN) -> DefPath
 197     where
 198         FN: FnMut(DefIndex) -> DefKey,
 199     {
 200         let mut data = vec![];
 201         let mut index = Some(start_index);
 202         loop {
 203             debug!("DefPath::make: krate={:?} index={:?}", krate, index);
 204             let p = index.unwrap();
 205             let key = get_key(p);
 206             debug!("DefPath::make: key={:?}", key);
 207             match key.disambiguated_data.data {
 208                 DefPathData::CrateRoot => {
 209                     assert!(key.parent.is_none());
 210                     break;
 211                 }
 212                 _ => {
 213                     data.push(key.disambiguated_data);
 214                     index = key.parent;
 215                 }
 216             }
 217         }
 218         data.reverse();
 219         DefPath { data, krate }
 220     }
 221
 222     /// Returns a string representation of the `DefPath` without
 223     /// the crate-prefix. This method is useful if you don't have
 224     /// a `TyCtxt` available.
 225     pub fn to_string_no_crate_verbose(&self) -> String {
 226         let mut s = String::with_capacity(self.data.len() * 16);
 227
 228         for component in &self.data {
 229             write!(s, "::{}", component).unwrap();
 230         }
 231
 232         s
 233     }
 234
 235     /// Returns a filename-friendly string of the `DefPath`, without
 236     /// the crate-prefix. This method is useful if you don't have
 237     /// a `TyCtxt` available.
 238     pub fn to_filename_friendly_no_crate(&self) -> String {
 239         let mut s = String::with_capacity(self.data.len() * 16);
 240
 241         let mut opt_delimiter = None;
 242         for component in &self.data {
 243             s.extend(opt_delimiter);
 244             opt_delimiter = Some('-');
 245             write!(s, "{}", component).unwrap();
 246         }
 247
 248         s
 249     }
 250 }
 251
 252 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, Encodable, Decodable)]
 253 pub enum DefPathData {
 254     // Root: these should only be used for the root nodes, because
 255     // they are treated specially by the `def_path` function.
 256     /// The crate root (marker).
 257     CrateRoot,
 258     // Catch-all for random `DefId` things like `DUMMY_NODE_ID`.
 259     Misc,
 260
 261     // Different kinds of items and item-like things:
 262     /// An impl.
 263     Impl,
 264     /// Something in the type namespace.
 265     TypeNs(Symbol),
 266     /// Something in the value namespace.
 267     ValueNs(Symbol),
 268     /// Something in the macro namespace.
 269     MacroNs(Symbol),
 270     /// Something in the lifetime namespace.
 271     LifetimeNs(Symbol),
 272     /// A closure expression.
 273     ClosureExpr,
 274
 275     // Subportions of items:
 276     /// Implicit constructor for a unit or tuple-like struct or enum variant.
 277     Ctor,
 278     /// A constant expression (see `{ast,hir}::AnonConst`).
 279     AnonConst,
 280     /// An `impl Trait` type node.
 281     ImplTrait,
 282 }
 283
 284 impl Definitions {
 285     pub fn def_path_table(&self) -> &DefPathTable {
 286         &self.table
 287     }
 288
 289     /// Gets the number of definitions.
 290     pub fn def_index_count(&self) -> usize {
 291         self.table.index_to_key.len()
 292     }
 293
 294     #[inline]
 295     pub fn def_key(&self, id: LocalDefId) -> DefKey {
 296         self.table.def_key(id.local_def_index)
 297     }
 298
 299     #[inline(always)]
 300     pub fn def_path_hash(&self, id: LocalDefId) -> DefPathHash {
 301         self.table.def_path_hash(id.local_def_index)
 302     }
 303
 304     /// Returns the path from the crate root to `index`. The root
 305     /// nodes are not included in the path (i.e., this will be an
 306     /// empty vector for the crate root). For an inlined item, this
 307     /// will be the path of the item in the external crate (but the
 308     /// path will begin with the path to the external crate).
 309     pub fn def_path(&self, id: LocalDefId) -> DefPath {
 310         DefPath::make(LOCAL_CRATE, id.local_def_index, |index| {
 311             self.def_key(LocalDefId { local_def_index: index })
 312         })
 313     }
 314
 315     #[inline]
 316     #[track_caller]
 317     pub fn local_def_id_to_hir_id(&self, id: LocalDefId) -> hir::HirId {
 318         self.def_id_to_hir_id[id].unwrap()
 319     }
 320
 321     #[inline]
 322     pub fn opt_hir_id_to_local_def_id(&self, hir_id: hir::HirId) -> Option<LocalDefId> {
 323         self.hir_id_to_def_id.get(&hir_id).copied()
 324     }
 325
 326     /// Adds a root definition (no parent) and a few other reserved definitions.
 327     pub fn new(stable_crate_id: StableCrateId) -> Definitions {
 328         let key = DefKey {
 329             parent: None,
 330             disambiguated_data: DisambiguatedDefPathData {
 331                 data: DefPathData::CrateRoot,
 332                 disambiguator: 0,
 333             },
 334         };
 335
 336         let parent_hash = DefPathHash::new(stable_crate_id, 0);
 337         let def_path_hash = key.compute_stable_hash(parent_hash);
 338
 339         // Create the root definition.
 340         let mut table = DefPathTable::default();
 341         let root = LocalDefId { local_def_index: table.allocate(key, def_path_hash) };
 342         assert_eq!(root.local_def_index, CRATE_DEF_INDEX);
 343
 344         Definitions {
 345             table,
 346             def_id_to_hir_id: Default::default(),
 347             hir_id_to_def_id: Default::default(),
 348             expansions_that_defined: Default::default(),
 349         }
 350     }
 351
 352     /// Retrieves the root definition.
 353     pub fn get_root_def(&self) -> LocalDefId {
 354         LocalDefId { local_def_index: CRATE_DEF_INDEX }
 355     }
 356
 357     /// Adds a definition with a parent definition.
 358     pub fn create_def(
 359         &mut self,
 360         parent: LocalDefId,
 361         data: DefPathData,
 362         expn_id: ExpnId,
 363         mut next_disambiguator: impl FnMut(LocalDefId, DefPathData) -> u32,
 364     ) -> LocalDefId {
 365         debug!("create_def(parent={:?}, data={:?}, expn_id={:?})", parent, data, expn_id);
 366
 367         // The root node must be created with `create_root_def()`.
 368         assert!(data != DefPathData::CrateRoot);
 369
 370         let disambiguator = next_disambiguator(parent, data);
 371         let key = DefKey {
 372             parent: Some(parent.local_def_index),
 373             disambiguated_data: DisambiguatedDefPathData { data, disambiguator },
 374         };
 375
 376         let parent_hash = self.table.def_path_hash(parent.local_def_index);
 377         let def_path_hash = key.compute_stable_hash(parent_hash);
 378
 379         debug!("create_def: after disambiguation, key = {:?}", key);
 380
 381         // Create the definition.
 382         let def_id = LocalDefId { local_def_index: self.table.allocate(key, def_path_hash) };
 383
 384         if expn_id != ExpnId::root() {
 385             self.expansions_that_defined.insert(def_id, expn_id);
 386         }
 387
 388         def_id
 389     }
 390
 391     /// Initializes the `LocalDefId` to `HirId` mapping once it has been generated during
 392     /// AST to HIR lowering.
 393     pub fn init_def_id_to_hir_id_mapping(
 394         &mut self,
 395         mapping: IndexVec<LocalDefId, Option<hir::HirId>>,
 396     ) {
 397         assert!(
 398             self.def_id_to_hir_id.is_empty(),
 399             "trying to initialize `LocalDefId` <-> `HirId` mappings twice"
 400         );
 401
 402         // Build the reverse mapping of `def_id_to_hir_id`.
 403         self.hir_id_to_def_id = mapping
 404             .iter_enumerated()
 405             .filter_map(|(def_id, hir_id)| hir_id.map(|hir_id| (hir_id, def_id)))
 406             .collect();
 407
 408         self.def_id_to_hir_id = mapping;
 409     }
 410
 411     pub fn expansion_that_defined(&self, id: LocalDefId) -> ExpnId {
 412         self.expansions_that_defined.get(&id).copied().unwrap_or_else(ExpnId::root)
 413     }
 414
 415     pub fn iter_local_def_id(&self) -> impl Iterator<Item = LocalDefId> + '_ {
 416         self.def_id_to_hir_id.iter_enumerated().map(|(k, _)| k)
 417     }
 418
 419     #[inline(always)]
 420     pub fn local_def_path_hash_to_def_id(&self, hash: DefPathHash) -> Option<LocalDefId> {
 421         self.table
 422             .def_path_hash_to_index
 423             .get(&hash)
 424             .map(|&local_def_index| LocalDefId { local_def_index })
 425     }
 426 }
 427
 428 #[derive(Copy, Clone, PartialEq, Debug)]
 429 pub enum DefPathDataName {
 430     Named(Symbol),
 431     Anon { namespace: Symbol },
 432 }
 433
 434 impl DefPathData {
 435     pub fn get_opt_name(&self) -> Option<Symbol> {
 436         use self::DefPathData::*;
 437         match *self {
 438             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
 439
 440             Impl | CrateRoot | Misc | ClosureExpr | Ctor | AnonConst | ImplTrait => None,
 441         }
 442     }
 443
 444     pub fn name(&self) -> DefPathDataName {
 445         use self::DefPathData::*;
 446         match *self {
 447             TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => {
 448                 DefPathDataName::Named(name)
 449             }
 450             // Note that this does not show up in user print-outs.
 451             CrateRoot => DefPathDataName::Anon { namespace: kw::Crate },
 452             Impl => DefPathDataName::Anon { namespace: kw::Impl },
 453             Misc => DefPathDataName::Anon { namespace: sym::misc },
 454             ClosureExpr => DefPathDataName::Anon { namespace: sym::closure },
 455             Ctor => DefPathDataName::Anon { namespace: sym::constructor },
 456             AnonConst => DefPathDataName::Anon { namespace: sym::constant },
 457             ImplTrait => DefPathDataName::Anon { namespace: sym::opaque },
 458         }
 459     }
 460 }
 461
 462 impl fmt::Display for DefPathData {
 463     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 464         match self.name() {
 465             DefPathDataName::Named(name) => f.write_str(&name.as_str()),
 466             // FIXME(#70334): this will generate legacy {{closure}}, {{impl}}, etc
 467             DefPathDataName::Anon { namespace } => write!(f, "{{{{{}}}}}", namespace),
 468         }
 469     }
 470 }